Die-quenched crankshaft

ABSTRACT

A die-quenching apparatus having relatively movable upper and lower opposed platens with a plurality of opposed workpieceengaging die blocks attached to said platens and a plurality of protruding pads circumferentially located at spaced intervals about the inner surface of each of said opposing die blocks. The opposed platens have internal cavities for the transmission of quenching fluid to the workpiece and said die blocks and pads are passageways extending therethrough and providing fluid communication between said platen cavities and said workpiece.

United States Patent Inventors Raymond H. Hays Peoria; Jack E. Sansom,Eureka; Kenneth D. Gladden, Washington, all of. 111.

Appl. No, 871,169

Filed Nov. 5, 1969 Division of Ser. No. 553.142. .\1a v 26, 1966. Pat.No. 3.506.501.

Patented June 29, 1971 Assignee Caterpillar Tractor Co.

Peoria, 111.

DIE-QUENCHED CRANKSHAFT 4 Claims, 7 Drawing Figs.

U.S. C1 266/6, 148/146 Int. Cl C2ld 1/62 Field of Search ..f 266/6 PC,

[ 56] References Cited UNITED STATES PATENTS 1,337,465 4/1920 Clson266/6 1,448,878 3/1923 Smith 266/6 2,255,103 9/1941 Denneen et a1 266/42,492,434 12/1949 Mueller 266/6 2,574,564 11/1951 Hogel et a1. 266/43,033,548 5/1962 French 266/6 3,294,597 12/1966 Kuchera 148/143 PrimaryExaminer-Gerald A. Dost Attorney-Fryer, Tjensvold, Feix, Phillips &Lempio ro o 0 054106?) PATENTEU JUH29 l9?! SHEET 1 0F 3 m. m w TAWM mamM H w T WW Mm DnJK AT TORN EYS DIlE-QUENCHED CRANKSHAFT This applicationis a division of application Ser. No. 553,142, filed May 26, 1966, nowU.S. Pat. No. 3,506,501.

This invention relates to a new improved die-quench hardened crankshaftand die-quenching apparatus and method for producing the same.

The current commercial practice of processing forges steel crankshaftsis to heat and quench the entire surface for grain refinement andsubsequently temper for producing a machineable hardness. After coldstraightening and basic machining, the hearing surfaces are inductionhardened, reheated to tempering temperature, and then finally finishground. In some cases the bearing fillets are shot peened prior to finalfinishing to increase fatigue strength.

Several problems have led to the need for the present invention, each ofwhich has more or less intensified the other. The first of these is therapidly increasing gas pressures in modern diesel engines as a result ofthe constant demand for increased horsepower from an engine of givensize. These pressures not only add further loading to the crankshaft butalso excite more rigorous vibrations which add to crankshaft fatigue. Itis, therefore, desirable to provide a crankshaft which would be strongerat its present size and weight without using more expensive alloysteels. Toward this end, attempts have been made to provide the strongercrankshaft by heat treatment.

Unfortunately, heat treatment per se causes several problems, especiallywith an article of such irregular shape as a crankshaft. One suchproblem is that in the use ofexisting induction heat-treatment methods,it is necessary to use a steel of high carbon content to get the depthof hardness which is needed for overall shaft strength and properbearing life. A phenomenon which may be termed longitudinal cracking hasoccurred in engines utilizing relatively high carbon crankshafts. Suchlongitudinal cracks develop in the journal surface of the crankshaftduring engine operation as a result of the adverse stresses producedfrom heat generated during bearing seizures. These cracks start a stresspoint which can lead to ultimate failure of the crankshaft.

During the past few years, the tempering temperature of the crankshaftshas been raised from 540 to 740 F. to increase the ductility in thecrank surface to prevent longitudinal cracking in field service and,unfortunately, the hardness level has been lowered from Rockwell C49--57 to the present Rockwell C 40-46. This in turn has reduced thefatigue strength and wear-life of the crankshafts.

A further problem is that if a complete crankshaft is heated andimmediately quenched in an open quenching tank, distortion is so greatthat considerable time is consumed is straightening the cold crankshaftto make it usable. This is not only objectionable from a cost standpointbut it has been proven that when a piece of steel is straightenedfollowing heat treatment, some" areas are structurally weakened. In manycases, the distortions so great that it cannot be corrected within thedesired limits.

Also in present induction hardening processes it is often necessary thatoil holes in the crankshaft be plugged to prevent cracks from formingtherein during the quenching operation. After the subsequent inductionhardening process, the crankshafts are again straightened and a peeningopera tion is done in the area of the pin and main journals. Thisoperation is necessary on present production crankshafts to alleviateundesirable residual stresses causes by the sharp transition between thehardened and relatively unhardened portions of the crankshaft formed bythe induction hardening in the fillet area. This tends to relieve thestressed area between the hardened portion of the bearing surfaces andthe fillets andeliminate cracks that generally start in this area if nopeening is done.

The present invention provides a low carbon content crankshaft which iscompletely die-quench hardened after substantially all machiningoperations have been performed thereon and which eliminates the need forthe straightening process previously required, the shot peeningoperation, and the plugging of the crankshaft oil holes. Since lowcarbon quenched and tempered steels are tougher than high carbon steelsat the same hardness level, it is possible to use a low carbon steel ata higher hardness level with no increase in susceptibility tolongitudinal cracking, but with marked improvement in fatigue life. As aresult of the invention, the final crankshaft hardness is of a highervalue, such as Rockwell C 49--54, than that attainable previouslywithout encountering cracking problems, etc. Further, as a result of thenovel diequenching apparatus of the present invention, it is possible toharden the entire surface of the crankshaft since when placed within thedie the crankshaft is straightened and properly held while jets of waterunder pressure drastically quench the journals, thereby achieving anexcellent surface hardening pattern. While the quenching process istaking place, the entire fixture and crankshaft are submerged and, dueto the greatly agitated water from the jets, the hardness pattern iscontinued out into the cheeks and/or throws of the crankshaft.

The previously required cold straightening operation, the shot peeningoperation, and the need for plugging the oil holes have all beeneliminated as a result of the invention. The straightening operation hasbeen eliminated as a result of the novel die-quenching apparatus whichproperly retains the crankshaft during the quenching operation. Thevarious other operations are eliminated since the extreme agitation ofthe water and jets against the retained crankshaft distribute the heattreat pattern evenly throughout the entire exposed surfaces of thecrankshaft. Any changes between the hardened surfaces and relativelyunhardened surfaces are gradual so as to eliminate the sharp stressconcentrations known to crankshafts produced by prior art procedures.

In addition to the advantage of eliminating such previously requiredoperations are straightening after quenching, shot peening and oil holeplugging, the low carbon content diequench hardened crankshaft of thepresent invention has numerous other advantages such as increasedfatigue life, higher surface harness, elimination or longitudinal stresscracking, greater core strength and quench hardened fillets. Moreover, amore economical grade of steel can be used than was previously possible.

Other objects and advantages of the invention will become more readilyapparent from the following detailed description when taken inconjunction with the accompanying drawing.

In the drawing:

FIG. 1 is a side elevation of one embodiment of diequenching apparatusconstructed in accordance with the invention;

FIG. 2 is a partial cross section taken on the line IIII of FIG. 1;

FIG. 3 is a plan view taken on the line III-III of FIG. 2;

FIG. 4 is a cross sectional view taken on the line IV-IV of FIG. 2;

FIG. 5 is a longitudinal view, partially in section, of a modifiedembodiment of die-quenching apparatus constructed in accordance with theinvention;

FIG. 6 is a cross-sectional view taken on the line VI-VI of FIG. 5; and,

FIG. 7 is a cross-sectional view taken on the line VII-VII of FIG. 5.

Referring now to FIG. 1, the die-quenching apparatus of the inventioncomprises a movable upper platen 10 adapted to cooperate with a worksupporting lower platen 12. The platens I0 and 12 are respectivelyprovided with a plurality of upper 14 and lower 16 die blocks which areadapted to receive therebetween a cylindrical workpiece such as themultithrow crankshaft 18, on which the quenching operation is to beperformed. It is to be noted that although the die blocks are of likeconstruction, they are of different heights and in different locations,to secure the respective journals of crankshaft 18 in proper position.The lower platen 12 is provided with a plurality, preferably four, ofspring-loaded buttons 20 which support the crankshaft by its cheeks 22when it is first placed in the apparatus. The buttons 20 prevent thecrankshaft journals 24 from coming into contact with the cold metal ofthe die blocks 16 until the upper platen I is lowered into place forcommencement of the straightening and quenching operation. Contact ofthe hot journals with the relatively cold die blocks for any length oftime prior to application of the quench water effects a mild quench ofthe contact area and is detrimental to the quenching operation.

Referring now to FIG. 2 in conjunction with FIG. 1, it can be seen thatthe platens l0 and 12 and die blocks 14 and 16 are of hollowconstruction, the die blocks being secured to the platens by suitableretaining means 26 and alignment pins 28. A plurality of conduits asindicated at 30 and 32, are connected to the platens allowing waterunder pressure to be directed through the platens to the die blocks.

As shown in FIGS. 2, 3 and 4, the upper die blocks 14 and lower dieblocks 16 have generally cylindrically shaped opposed surfaces 34 forsubstantially surrounding the crankshaft 18 when the platens are inclosed position. Two or more protruding pads 36 are suitably spacedabout each die block surface for contact with and support of thecrankshaft journals 24. Suitable retaining bolts 38 (see FIG. 4) areprovided for securing and adjusting the pads 36 with respect to theirrespective die blocks. Shims 40 can be removed or added between the padsand their respective blocks so as to shift the workpiece eitherlaterally or vertically. As shown, a plurality of small passageways 42are provided in both the cylindrical surfaces 34 of the die blocks andthe pads 36 to allow jets of water during the quenching operation tocontact as much of the crankshaft journal surfaces as possible. It isimportant that the external surfaces of the pads 36 be shaped so as tomake minimal contact the journals during the quenching operation.Although the pads are shown with accurately shaped external surfaces,these surfaces could be of any other suitable shape such, for example,as triangular with radiused corners providing the support for thevariousjournals.

In the modified embodiment shown in FIGS. 7, the upper platen 50 andlower platen 51 receive water through ports 52. Suitably secured to eachof the platens, and in fluid communication therewith, are supportingblocks 54 and 56. Upper and lower die blocks 58 and 60 are secured totheir respective supporting blocks by retaining bolts 62, the bolt headsof which are accessible thorough normally plugged apertures 64. Itshould be noted that the pads 66 are an integral part of the die blocks58 and 60. During the quenching operation, water under high pressureenters port 52, flows through drilled passages 68 into the die blockcavity 70 and outwardly through holes 72 to spray against the crankshaftjournals.

Since the pads 66 are integrally formed on the die blocks, lateral andvertical adjustment thereof must be made via the die blocks 58 and 60.The die blocks are adjusted vertically by changing shims 74 locatedbetween the die blocks and their respective supporting blocks. As bestshown with reference to the lower platen 51 (FIGS. 5 and 7), an invertedT-shaped bracket 75 is fastened to the lower platen by means of bolts 76and alignment pins 78. Located at the midportion of the bar of theT-shaped bracket is a bifurcated leg 80 which closely receives thesupport block 56. lntegrally formed on the support block 56 are a pairof spaced arms 82 which straddle the leg 80 of bracket 75. The supportblock 56 is adjustably secured to the bracket 75 by means of fasteners84 adapted to be received in oversized holes 86 formed in the arms 82.It will be readily understood that after loosening fasteners 84 the0.200 inches (as measured five Rockwell C points below the surfacehardness). Test results have indicated that the above crankshafts, whendie-quenched in the apparatus of the invention, have a Total IndicatorRunout ofless than 0.020 inches.

In operation, immediately after the crankshaft has been furnace heatedto its austenitizing temperature, it is placed in the lower platen andsupported above the lower die blocks by the spring-loaded buttons. Thebuttons prevent the crankshaft journals from coming into contact withthe die pads until a very short time prior to the beginning of thequenching cycle. The upper die is then moved into position forcing thespringloaded buttons downwardly which allows the crankshaft to beclamped in position as shown in FIGS. 2 and 5.

With the crankshaft clamped in position and with the entire quenchingapparatus placed in a tank (not shown), fluid quenchant, preferablywater under very high pressure, is directed through the hollow platensand sprayed through the many passages in the dies against the crankshaftjournals and fillets. Immediately following the beginning of thequenching spray, the entire crankshaft is submerged and subjected to adrastic-quench so as to cause the hardness case to be extended over theentire crankshaft. Due to the extreme agitation of the water against theretained crankshaft, the heat treat pattern is distributed evenlythroughout the entire exposed surfaces of the crankshaft including theoil hole surfaces inside the crankshaft. It is to be understood that thesubmersion process could be eliminated by providing sufficient waterjets in the die-quenching apparatus to spray the entire crankshaft.

We claim:

1. Die-quenching apparatus comprising relatively movable upper and loweropposed platens; a plurality of die blocks supported on said upperplaten; a corresponding plurality of lower die blocks supported on saidlower platen for mating cooperation with said upper die blocks; saidupper and lower die blocks each having an internal cavity and furtherhaving generally cylindrical opposed outer surfaces for receiving andsubstantially surrounding a workpiece when said platens are moved towardeach other; a plurality of protruding workpiece supporting padscircumferentially located at spaced locations about the cylindricalsurface of each of said die blocks; said workpiece supporting padshaving generally arcuate outer surfaces for establishing minimal surfacecontact with said workpiece; and a plurality of relatively small fluidpassageways extending through both the cylindrical surfaces of said dieblocks and said workpiece supporting pads, said passageways providingfluid communication with said die block cavities.

2. Die-quenching apparatus as set forth in claim 1 and furthercomprising a plurality of button means resiliently supported on saidlower platen for preventing contact between a workpiece placed thereonand the protruding workpiece supporting pads on said lower die blockwhen said upper and lower platens are moved away from each other.

3. Die-quenching apparatus as set forth in claim 2 and furthercomprising means for radially adjusting said workpiece supporting padsrelative to their respective die blocks.

4. Die-quenching apparatus as set forth in claim 2 and further includingmeans for adjusting said die blocks both horizontally and verticallyrelative to said platens.

@333? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3#569,597 Dated June 29, 1971 Invenmfls) RAYMOND HAYS; JACK E. SANSOM.KENNETH D. GLADDEN It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Kbstract, line 8, after "are", insert --provided with a plurality ofrelatively small fluid--.

Column 1, line 13, "hearing" should read --bearing--.

Column 1, line 57, delete "distortions" and insert ---distortion is--.

Signed and sealed this 28th day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK Commissioner of PatentsAttesting Officer

1. Die-quenching apparatus comprising relatively movable upper and loweropposed platens; a plurality of die blocks supported on said upperplaten; a corresponding plurality of lower die blocks supported on saidlower platen for mating cooperation with said upper die blocks; saidupper and lower die blocks each having an internal cavity and furtherhaving generally cylindrical opposed outer surfaces for receiving andsubstantially sUrrounding a workpiece when said platens are moved towardeach other; a plurality of protruding workpiece supporting padscircumferentially located at spaced locations about the cylindricalsurface of each of said die blocks; said workpiece supporting padshaving generally arcuate outer surfaces for establishing minimal surfacecontact with said workpiece; and a plurality of relatively small fluidpassageways extending through both the cylindrical surfaces of said dieblocks and said workpiece supporting pads, said passageways providingfluid communication with said die block cavities.
 2. Die-quenchingapparatus as set forth in claim 1 and further comprising a plurality ofbutton means resiliently supported on said lower platen for preventingcontact between a workpiece placed thereon and the protruding workpiecesupporting pads on said lower die block when said upper and lowerplatens are moved away from each other.
 3. Die-quenching apparatus asset forth in claim 2 and further comprising means for radially adjustingsaid workpiece supporting pads relative to their respective die blocks.4. Die-quenching apparatus as set forth in claim 2 and further includingmeans for adjusting said die blocks both horizontally and verticallyrelative to said platens.